U.N. High Commissioner for Human Rights Zeid Ra’ad al-Hussein says the siege and bombardment of Syria’s northern city of eastern Aleppo constitute crimes of historic proportions. He is calling on the 47-member U.N. Human Rights Council to refer the situation to the International Criminal Court.

Zeid says well over 300,000 Syrians have been killed and countless others wounded and traumatized in the course of more than five years of civil war. He says the relentless bombardment of Aleppo has turned the ancient city into a slaughterhouse.

Without mentioning Russia by name, the high commissioner blames the indiscriminate airstrikes across the eastern rebel-held part of Aleppo by government forces and their allies for the overwhelming majority of civilian casualties.

He says the violations constitute war crimes and calls for those guilty of international crimes to be held accountable.

Paulo Sergio Pinheiro, chair of the International Commission of Inquiry on Syria, agrees all parties to the conflict guilty of crimes must be brought to justice.

“Perpetrators of war crimes and crimes against humanity will only cease to violate the laws of war when it is clear they will be held to account," he said. "This why referral of the conflict in Syria to the ICC (International Criminal Court) or an ad hoc international justice mechanism is critical to resolving this conflict.”

People remove belongings from a damaged site after an air strike Sunday in the rebel-held besieged al-Qaterji neighbourhood of Aleppo, Syria, Oct. 17, 2016.

Pinheiro says members of the investigative commission will continue to document war crimes in Aleppo. The British minister for Africa and the Middle East, Tobias Ellwood, launched a blistering attack on Syria and Russia.

“Hospitals have been bombed repeatedly. Hundreds of civilians, many of them children, have been killed since the (Bashar) Assad regime and Russia launched their assault on Eastern Aleppo.”

The Russian ambassador accuses Britain and its allies of protecting terrorists from destruction and allowing them to regroup so they can continue what he calls their barbaric acts. The Syrian representative calls Britain’s accusations baseless and fabricated to enhance its political agenda.